Regarding the involvement of demons in monastic dreams, St. John Climacus reflects on this matter as follows:
“When we, leaving our homes and relatives for the sake of the Lord, dedicate ourselves to a life of solitude out of love for God, the demons try to disturb us with dreams, showing us our relatives grieving, dying, or suffering trials because of us. Therefore, the one who believes in dreams is like a person chasing his own shadow, trying to catch it.”
The demons of vanity become prophets in dreams. In their cunning and deceit, they observe certain signs and conclude what will happen, then reveal it to us beforehand so that we may marvel when the dreams come true in reality, and begin to think highly of ourselves—as if we are already close to the gift of foresight. Such a person often becomes a prophet in the eyes of those who believe in demons. For those who despise demons, he is always a liar. Being a spirit, the demon sees what happens in the air. Noticing, for example, that someone is dying, he foretells the event in a dream to the weak-hearted. However, demons know nothing of the future by foreknowledge. After all, even doctors are able to predict death!
Often, demons transform themselves into angels of light and take on the appearance of martyrs, showing us in dreams that we approach them. When we wake up, they fill us with joy and pride. This serves as a sign that we have been deceived. For when angels appear, they depict eternal torments, the Terrible Judgment, and the expulsion from the Kingdom of God, and those who wake up from such a dream are filled with trembling and contrition.
If we begin to obey them in dreams, the demons will mock us even while awake. A person who believes in dreams is completely inexperienced. Wise is the one who does not believe them at all. Believe only in those dreams that reveal eternal torments and the Terrible Judgment to you. But if they lead you to despair, then they too are from demons.
St. John Cassian tells of a monk from Mesopotamia who led a very solitary and ascetic life but perished because of the deception of demonic dreams. Seeing that the monk paid little attention to his spiritual perfection and was entirely devoted to bodily asceticism, valuing his own effort and attributing merit to it, demons began to show him dreams that, by their cunning, came true. When the monk became firm in his belief in his dreams and in himself, the devil, in a magnificent vision, showed him the Jews enjoying heavenly bliss and the Christians suffering in hellish torments. The demon—naturally in the guise of an angel or one of the Old Testament righteous—advised the monk to embrace Judaism so that he might partake in the bliss of the Jews, which the monk, without the slightest hesitation, did. This account is more than sufficient to explain to our beloved brothers how foolish it is to believe in dreams and what terrible harm can arise from such belief. When we pay attention to dreams, faith in them subtly infiltrates the soul, and therefore it is strictly forbidden to pay attention to them.
The nature, renewed by the Holy Spirit, is guided by entirely different laws than the nature that has fallen and remains entrenched in its fall. The Holy Spirit guides the renewed man. “They are enlightened by the grace of the Divine Spirit,” says St. Macarius of Egypt, “and it dwells in the depths of their mind: for such people, the Lord is like their very soul.” Both in wakefulness and in sleep, they remain in the Lord, apart from sin, beyond earthly and bodily thoughts and imaginations. Their thoughts and dreams, which during sleep are not under the control of human reason and will, and which in others operate unconsciously according to the demands of nature, are in them guided by the Spirit, so the dreams of such people have spiritual significance. Thus, the righteous Joseph was taught in a dream about the mystery of the Incarnation of the Logos; in a dream, he was commanded to flee to Egypt and then to return from there (Matthew 1-2). The dreams sent by God possess an unshakeable conviction. This conviction is understandable and comprehensible to God’s Saints, but it is unattainable for those who are still engaged in the struggle with passions.
When you lie down to sleep, you should remember death, whose image is the temporary sleep, and renouncing all thoughts and imaginations, fall asleep with the Jesus Prayer on your lips.
